Zinc lanthanide sulfonic acid electrolytes

ABSTRACT

Disclosed are aqueous solutions for use in high energy, highly efficient electrical energy storage devices. The solutions contain (a) a high purity sulfonic acid with a low concentration of low valent sulfur compounds or higher valent sulfur compounds susceptible to reduction, (b) a metal or metals in an oxidized state that are capable of being reduced to the zero valent oxidation state, (c) a metal that is in an oxidized state that is incapable of being reduced to its metallic state and (d) optionally, a buffering agent and/or conductivity salts.

This application claims the benefit of U.S. Provisional Application Ser.No. 60/471,654 filed May 19, 2003.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the use of high purity metal sulfonicacids for use in energy storage devices, methods for preparing highpurity metal sulfonic acids electrolytes, methods for efficiently usingthe metal sulfonic acid solution and products formed by using suchmethods and solutions. More particularly, the invention providessulfonic acid solutions that have high cathode efficiencies for 2Bseries metals such as zinc deposition processes, sulfonic acid solutionsthat affords high solubility to lanthanide series ions and sulfonic acidsolutions that have low concentrations of low-valent sulfur compounds orhigher valent sulfur compounds susceptible of reduction that are capableof producing an unwanted odor during electrolysis.

2. Prior Art

Electrochemical processes are used in many large-scale stationary energydevice storage applications. The rating of an energy storage device isdependent upon the overall power supply and the discharge time. Powersupply can vary from 1 kilowatt (1 kW) in metal-air type batteries togreater than 1 gigawatt (1 GW) in pumped hydro-type batteries. Dischargetimes may also vary from a fraction of a second to greater than severalhours.

Improved reliability or power quality of energy storage devices mayrequire virtually uninterrupted power supplies (UPS). Such electricalstorage processes include capacitors, and super conducting magneticenergy storage devices. During a power interruption, these devices areused within fractions of a second to ensure an uninterrupted source ofpower.

Storage devices may also be used from a few seconds to several minutesin cases where the power is switched from one main power supply (e.g., apower grid) to another main power supply.

Electrical energy storage devices may also be used to provide costsavings to large users in times of limited available power. Such powerdevices provide sufficient electrical energy from minutes to hours induration to meet peak energy demands, or to provide a reservoir of powerfor use in off-peak times.

The capability of the energy storage process and the accompanying poweroutput is dependent upon the engineering design of the device,composition of the electrolytes used in such device and the type ofpower rating needed. There are several commercial energy storageprocesses available each with its own advantages and disadvantages.These include the polysulfide bromide battery (PSB), the vanadium redoxbattery (VRB), the zinc bromine battery (ZnBr), the sodium sulfidebattery (NaS), lithium ion battery, compressed air energy storage(CAES), large-scale lead acid battery (LSLA), pumped hydro, E.C.capacitors and flywheel technologies.

There are three flow-type batteries, PSB, VRB and ZnBr. The PSB batteryemploys two sodium electrolytes, sodium bromide and sodium sulfide. Theredox potential of this cell is about 1.5 V and the efficiency isapproximately 75%. The VRB use two cell each containing vanadium. In onecell, V⁺²/V⁺³ is used and in the other, V⁺⁴/V⁺⁵. The redox voltage isabout 1.4 to 1.6 V and the efficiency is slightly higher than the PSBbattery, about 85%. The ZnBr redox potential is about 1.8 V yet theefficiency is only about 75%. All these flow-type batteries haverelatively high power ratings and may be used in energy management typeapplications where supplemental power is needed over an extended periodof time. All these flow-type batteries suffer from low energy density.

The NaS battery uses molten sulfur and molten sodium to produce a redoxvoltage of about 2 volts at an efficiency of approximately 88%. The maindrawbacks to this type of battery are the high temperature, 300° C.,necessary to keep the metals molten, safety concerns using thesematerials and high production costs.

The lithium-ion battery has efficiency near 100% and high energy densityand long life cycles. Although useful for small-scale applications, themain drawback to large-scale use is the inherently high cost, about$600/kWh.

CAES plants are capable of producing power in the GW range with longpower durations. However, the CAES plants are very expensive, on theorder of ten of millions of dollars and take several years to build sucha plant. The CAES plants are site-specific and may need natural gas as afuel.

Recently, a new redox energy storage device was introduced byElectrochemical Design Associates, the Plurion Redox Battery. Thisbattery uses mixed salts of zinc and cerium in methanesulfonic acid(MSA). The redox potential of this cell is an excess of 2 volts. Thisenergy storage device based on zinc and cerium salts was discussed by B.J. Dougherty and co-workers at the Electrical Energy Storage Applicationand Technology meeting, 2002 EESAT meeting(http://www.sandia.gov/EESAT/). There is no mention of the compositionof the cerium ion, (e.g., Ce⁺³ or Ce⁺⁴) in this paper.

MSA has been used in a variety of electrochemical process, most notablyin electrodeposition (e.g., plating) applications. While offeringadvantages over other organic and mineral acids, MSA (and other sulfonicacids) and the purity and composition of the metal-sulfonate electrolytemust be uniquely balanced to ensure a quality metal coating and a highelectrolytic efficient process.

The use of sulfonic acids in electrochemical applications, and inparticular, MSA, is not new. Proell, W. A. in U.S. Pat. No. 2,525,942claims the use of alkanesulfonic acid electrolytes in numerous types ofelectroplating. For the most part, Proell's formulations employed mixedalkanesulfonic acids of unspecified purity. In U.S. Pat. No. 2,525,942Proell made specific claims for lead, nickel, cadmium, silver and zinc.In another U.S. Pat. No. 2,525,943, Proell specifically claims the useof alkanesulfonic acid based electrolytes in copper electroplating andthe exact compositions and purity of the plating formulations were notdisclosed. In a separate publication (Proell, W. A.; Faust, C. L.;Agruss, B.; Combs, E. L.; The Monthly Review of the AmericanElectroplaters Society 1947, 34, 541-9) Proell describes preferredformulations for copper plating from mixed alkanesulfonic acid basedelectrolytes.

Martyak and co-workers in EP 0786539 A2 have discussed zinc depositionfrom MSA-based electrolytes. The acid electrolytes contained from about5 grams per liter to about 175 grams per liter of the zinc-sulfonatesalt. The pH described in this application claims the zinc sulfonatesolutions operate best at a pH from about 2.0 or greater and preferablyin the range from 3-5. The efficiency for zinc deposition is near 100%even at high current densities. Additives to the solution affected thequality of the zinc deposit. To minimize roughness in the zinc surface,it was necessary to use organic additives such as blocked and randomco-polymers of alkylene oxides.

The use of cerium in sulfonic acids was the scope of inventions by Krehand co-workers in U.S. Pat. Nos. 4,701,245 A1, 4,670,108 A1, 4,647,349A1 and 4,639,298 A1. The oxidation of organic compounds in these patentswas effected by the use of cerric compounds such as cerricmethanesulfonate and cerric trifluoromethanesulfonate. In all cases,oxidation was complete by only using cerium ion in its highest oxidationstate, Ce⁺⁴. The cerrous (Ce⁺³)/cerric (Ce⁺⁴) concentrations in MSA arecritical in maintaining a stable oxidizing environment. Theconcentration of cerium discussed in U.S. Pat. No. 4,639,298 is at least0.2 M but it does not differentiate between Ce⁺³ and Ce⁺⁴. Only the Ce⁺⁴ion is an oxidant and necessary in the MSA solution to effect theoxidation reaction. The concentration of free MSA is also important toassist in dissolving the cerium compounds and the preferredconcentrations of free MSA are from 1.5 M to about 9.0 M.

Thus, a new energy storage device based on zinc and cerium salts in asulfonic acid electrolyte leads to many challenges. A cathodic reactionof zinc ion to zinc metal must be balanced by the oxidation of cerrousion to cerric ion:Zn⁺²+2e ⁻→Zn^(o)2Ce⁺³→2Ce⁺⁴+2e ⁻

For every mole of zinc ion reduced at the cathode, two moles of cerricion are produced at the anode. Additional free acid is necessary in thisprocess to impart conductivity to the redox system and thus lower therequired voltage. However, as discussed in EP 0786539 A2, the pH forzinc deposition should be greater than 2.0 and preferably from 3-5. Theconcentration of zinc ion should also be high to achieve commerciallyacceptable deposition rates and smooth zinc coatings. Kreh andco-workers in U.S. Pat. No. 4,639,298 A1 discuss the use of high freesulfonic acid concentrations, greater than 1.5 M and preferably greaterthan 3.0 M. This high free sulfonic acid concentration necessary forcerium solubility, would result in a low pH, <1.0, and thus affect thezinc deposition process. The high free sulfonic acid concentration alsoaffects the solubility ratio of Ce⁺³/Ce⁺⁴.

It thus would be desirable to have new electrochemical energy storagedevices that contain compositions based on zinc and lanthanide seriessalts in sulfonic acids that produce high deposition efficiencies forzinc ion to zinc metal, free sulfonic acid to impart sufficientconductivity for the redox battery yet maintain high solubility oflanthanide series ion in solution to complete the redox couple.

It would be particularly desirable to have new sulfonic acidcompositions that can be effectively used with metals of strong reducingcapabilities such as zinc without deleterious effects such as odor oftenproduced when using sulfonic acids containing impurities capable ofproducing odor.

SUMMARY OF THE INVENTION

It has now been found that an new high energy, highly efficientelectrical energy storage device is possible when using metal saltspreferably of 2B series metal such as zinc and lanthanide series such ascerium in high purity sulfonic acids. This work focuses on theunexpected superiority of using high purity sulfonic acids with limitedfree acid concentration of the sulfonic acid concentration toeffectively dissolve zinc ion and lanthanide series ion.

Electrolytes of the invention are characterized in significant part bycomprising a low concentration of free sulfonic acid, <300 g/l. The lowfree sulfonic acid concentration allows for high cathode efficiency forzinc deposition yet is sufficient for solution conductivity. The lowfree sulfonic acid concentration also allows for increased solubility oflanthanide series ions.

Electrolytes of the invention are characterized in significant part bycomprising a low concentration of lanthanide series ion concentrationthat may precipitate from highly concentrated sulfonic acidelectrolytes.

Sulfonic acid electrolytes of the invention are also characterized insignificant part by comprising a low concentration of reduced sulfurcompounds or sulfur compounds in a higher oxidation state that aresusceptible to reduction, by either an active metal or duringelectrolysis, to low valent sulfur compounds (odor-causing impurities)such as sulfides, i.e. high purity. In particular, preferredelectrochemical compositions of the invention have a low concentrationof dimethyldisulfide, DMDS, (CH₃SSCH₃), dimethylsulfide, DMS, (CH₃SCH₃),dimethylsulfone, DMSO₂, (CH₃SO₂CH₃), trichloromethyl methylsulfone,TCMS, (CH₃SO₂CCl₃), dichloromethyl methylsulfone, DCMS, (CH₃SO₂CHCl₂),methyl methanethiosulfonate, MMTS, (CH₃SO₂SCH₃), and methylmethanesulfonate, MMS (CH₃SO₃CH₃).

In particular, preferred high purity sulfonic acids of the inventionhave a total concentration of reduced sulfur compounds less than about50 mg/liter, more preferably a total concentration of less than 10mg/liter, still more preferably less than 5 mg/liter.

The invention also includes articles of manufacture employing sulfonicacids of this invention, including batteries and other energy storagedevices.

DETAILED DESCRIPTION OF THE INVENTION

Compositions of the invention suitably contain a metal ion in a sulfonicacid electrolyte that is capable of being electrochemically reduced toits metallic state, a metal or metals that are in an oxidized state thatare incapable of being reduced to its metallic state, free sulfonic acidof high purity and optionally additives to enhance the zinc depositionreaction or increase the conductivity of the redox cell. The metal ionsare preferably added as metal salts of high purity sulfonic acid.

As discussed above, electrolytes of the invention are particularlyeffective in depositing 2B (series 2B of the Periodic Table) metal ionsuch as zinc ion from a sulfonic acid solution yet maintain a highlanthanide series (the lanthanide series of the Periodic Table) ionconcentration. In particular, sulfonic acid solutions of the inventionare useful in energy storage devices such as batteries.

Electrolytes of the invention generally comprise at least one soluble 2Bmetal salt, preferably zinc salt, one or more soluble lanthanide,preferably cerium, sulfonic acid salts, a high purity acid electrolyte,optionally a buffering agent and optionally conductivity salts. Moreparticularly, electrolyte compositions of the invention preferablycontain a zinc salt of a high purity alkyl or aryl sulfonic acid; alanthanide salt of a high purity alkyl or aryl sulfonic acid; a highpurity sulfonic acid electrolyte, preferably an acidic aqueous solutionsuch as a high purity alkyl or aryl sulfonic acid; optionally abuffering agent based on boric acid; optionally conductivity salts withthe anionic portion of the salt based on a high purity alkyl or arylsulfonic acid.

Zinc metal or a variety of zinc salts may also be in the zinc-lanthanideelectrolyte. Zinc sulfonate salts may be employed in the subjectsolutions wherein the sulfonic acid of the anionic portion of the zincsalt and any free acid are introduced as a high purity alkyl or arylsulfonic acid of formula:

wherein R, R′ and R″ are the same or different and each independentlymay be hydrogen, phenyl, Cl, F, Br, I, CF₃ or a lower alkyl group suchas (CH₂)n where n is from 1 to 7 and that is unsubstituted orsubstituted by oxygen, Cl, F, Br, I, CF₃, —SO₂OH. Preferred alkylsulfonic acids are methanesulfonic, ethanesulfonic and propanesulfonicacids and preferred alkyl polysulfonic acids are methanedisulfonic acid,monochloromethanedisulfonic acid, dichloromethanedisulfonic acid,1,1-ethanedisulfonic acid, 2-chloro-1,1-ethanedisulfonic acid,1,2-dichloro-1,1-ethanedisulfonic acid, 1,1-propanedisulfonic acid,3-chloro-1,1-propanedisulfonic acid, 1,2-ethylene disulfonic acid,1,3-propylene disulfonic acid, trifluoromethanesulfonic acid,butanesulfonic acid, perfluorobutanesulfonic acid, pentanesulfonic, andthe aryl sulfonic acids are phenylsulfonic, phenolsulfonic,paratoulenesulfonic, and xylenesulfonic acids. Zinc methanesulfonate isa particularly preferred zinc salt.

The zinc salt may be suitably present in a relatively wide concentrationrange in the electrolyte composition of the invention. Preferably, azinc salt will be employed at a concentration from about 5 to about 500grams per liter of solution, more preferably at a concentration of fromabout 20 to about 400 grams per liter of the solution, still morepreferably at a concentration of from about 40 to about 300 grams perliter of solution.

A variety of lanthanide salts such as cerium salts may also be in theelectrolyte. Lanthanide series sulfonate salts may be employed in thesubject solutions wherein the sulfonic acid of the anionic portion ofthe lanthanide series salt and any free acid are introduced as a highpurity alkyl or aryl sulfonic acid of formula:

wherein R, R′ and R″ are the same or different and each independentlymay be hydrogen, phenyl, Cl, F, Br, I, CF₃ or a lower alkyl group suchas (CH₂)n where n is from 1 to 7 and that is unsubstituted orsubstituted by oxygen, Cl, F, Br, I, CF₃, —SO₂OH. Preferred alkylsulfonic acid are methanesulfonic, ethanesulfonic and propanesulfonicacids and preferred alkyl polysulfonic acids are methanedisulfonic acid,monochloromethanedisulfonic acid, dichloromethanedisulfonic acid,1,1-ethanedisulfonic acid, 2-chloro-1,1-ethanedisulfonic acid,1,2-dichloro-1,1-ethanedisulfonic acid, 1,1-propanedisulfonic acid,3-chloro-1,1-propanedisulfonic acid 1,2-ethylene disulfonic acid,1,3-propylene disulfonic acid, trifluoromethanesulfonic acid,butanesulfonic acid, perfluorobutanesulfonic acid, pentanesulfonic, andthe aryl sulfonic acids are phenylsulfonic, phenolsulfonic,paratoulenesulfonic, and xylenesulfonic acids. Cerrous methanesulfonateand cerric methanesulfonate are a particularly preferred lanthanidesalts.

The preferred lanthanide series acid salt is cerium sulfonic acid saltand is suitably present in a relatively narrow concentration range inthe electrolyte of the invention. The individual concentrations of Ce⁺³and Ce⁺⁴ are governed by the concentration of free acid in the solution.

Preferably, a cerrous sulfonic acid salt will be employed at aconcentration from about 5 to about 800 grams per liter of solution,more preferably at a concentration of from about 20 to about 600 gramsper liter of solution, still more preferably at a concentration of fromabout 50 to about 300 grams per liter of solution.

A cerric sulfonic acid salt will be employed at a concentration fromabout 0.1 to about 100 grams per liter of solution, more preferably at aconcentration of from about 0.5 to about 50 grams per liter of solution,still more preferably at a concentration of from about 1 to about 25grams per liter of solution.

The electrolyte may also contain high purity free sulfonic acid toincrease solution conductivity. The preferred high purity free sulfonicacid has the same anion as the zinc and lanthanide series salt anion butmixtures of high purity free sulfonic acids are also within the scope ofthis invention. Preferred alkyl sulfonic acid are methanesulfonic,ethanesulfonic and propanesulfonic acids and preferred alkylpolysulfonic acids are methanedisulfonic acid,monochloromethanedisulfonic acid, dichloromethanedisulfonic acid,1,1-ethanedisulfonic acid, 2-chloro-1,1-ethanedisulfonic acid,1,2-dichloro-1,1-ethanedisulfonic acid, 1,1-propanedisulfonic acid,3-chloro-1,1-propanedisulfonic acid, 1,2-ethylene disulfonic acid,1,3-propylene disulfonic acid, trifluoromethanesulfonic acid,butanesulfonic acid, perfluorobutanesulfonic acid, pentanesulfonic acidand the aryl sulfonic acids are phenylsulfonic, phenolsulfonic,paratoulenesulfonic, and xylenesulfonic acids. The free acidconcentration ranges from about 1 to about 1480 grams per liter, morepreferably from about 10 to about 1200 grams per liter, still morepreferably from about 30 to about 300 grams per liter. The pH of theelectrolyte can vary between about 0.5 and 4 and more preferably betweenabout 2 and 3.

The buffering agents, if used, in the electrolyte solution can includeboric acid and/or tetraborate. The electrolyte solution containing thebuffering agents operate best at lower free acid concentrations, lessthan 300 grams per liter free acid and produce a smoother zinc coatingcompared to un-buffered electrolyte solutions. The concentration of thebuffering agent can range from about 0.1 g/l to saturation, morepreferably from about 1 g/l to about 75 g/l, still more preferably fromabout 5 g/l to about 50 g/l.

Conductivity salts, if used, in the electrolyte solution can includeammonium ions.

Sulfonic acid electrolytes of the invention are preferably employed ator above room temperature, e.g. up to and somewhat above 85° C. Thesulfonic acid solution may be agitated during use such as by using anair sparger, physical movement of the work piece, impingement or othersuitable methods.

Electrolysis is preferably conducted at a current ranging from 0.01 to150 ampere per dm² (A/dm²) depending upon the energy storage demand.

The invention described also includes the use of direct, pulse orperiodic current waveforms to effectively deposit a zinc layer on thecathode substrate.

A wide variety of substrates may be plated with zinc of the invention,as discussed above. The substrates include but are not limited to:carbon, steel, copper, aluminum or alloys of these metals.

The foregoing description of the invention is merely illustrativethereof, and it is understood that variations and modifications can beeffected without departing from the scope or spirit of the invention asset forth in the following claims.

EXAMPLES Example 1

This example shows the effects of free methanesulfonic acid on theconductivity of a solution containing low zinc ion concentration.Solutions of Zn(CH₃SO₃)₂ were prepared at a constant 32.5 gram per liter(g/l) Zn⁺² concentration and free CH₃SO₃H varying from 0 to 300 g/l.Each solution was heated to 65° C. and the conductivity recorded inmS/cm as shown in the following table.

32.5 g/l 32.5 g/l, 32.5 Zn⁺⁺, Zn⁺⁺, g/l Zn⁺⁺, 0 g/l 100 g/l 200 g/l 32.5g/l Zn⁺⁺, CH₃SO₃H CH₃SO₃H CH₃SO₃H 300 g/l CH₃SO₃H 20° C. 40.2 231 337366 25° C. 41.3 226 331 362 30° C. 41.4 220 324 355 35° C. 44.1 210 316350 40° C. 46.2 214 308 342 45° C. 49.9 201 302 338 50° C. 54.6 194.8296 330 55° C. 60.1 190 291 323 60° C. 65.2 185.1 287 313 65° C. 70.2180.5 282 308

The data shows an increase in conductivity with temperature for the zincion solution containing no free acid but a decrease in conductivity insolutions containing 100-300 g/l free acid. There is an increase inconductivity with free acid up to 300 g/l. The increase in conductivityis large when going from 0 to 100 g/l and from 100 to 200 g/l free acidbut there appears to be a diminishing return in conductivity when goingfrom 200 to 300 g/l free acid. Therefore, the zinc acid electrolyte canbe operated at 200 g/l free acid, or less, without significantdetrimental effects on conductivity.

Example 2

This example shows the effects of free methanesulfonic acidconcentration on the cathode efficiency for zinc deposition in solutionscontaining no lanthanide metals.

32.5 g/l Zn⁺⁺/100 g/l 32.5 g/l Zn⁺⁺/200 g/l 32.5 g/l Zn⁺⁺/300 g/l 32.5g/l Zn⁺⁺/0 g/l CH₃SO₃H CH₃SO₃H CH₃SO₃H CH₃SO₃H Original Weight 8.39818.2876 8.4798 8.3211 Final Weight 8.4874 8.3781 8.5452 8.3702 CathodeEfficiency (30 A/dm²) 87.91% 89.09% 64.38% 48.34% Appearance Light GrayLight Gray Light Gray Light Gray Cell Voltage 2.42 1.21 0.96 0.84Original Weight 8.4533 8.1982 8.2135 8.4224 Final Weight 8.6323 8.38918.3581 8.5577 Cathode Efficiency (60 A/dm²) 88.11% 93.97% 71.18% 66.60%Appearance Light Gray Light Gray Light Gray Light Gray Cell Voltage 4.412.25 1.7 1.61

Solutions of Zn(CH₃SO₃)₂ were prepared at a constant 32.5 g/l Zn⁺²concentration and free CH₃SO₃H varying from 0 to 300 g/l. Each solutionwas heated to 55° C. and the zinc was deposited on low carbon steel at30 A/dm² and 60 A/dm². The data in the above table shows the cathodeefficiency is high and commercially acceptable at 0 and 100 g/l freeacid but drops off only slightly at 200 g/l and considerably at 300 g/lfree methanesulfonic acid.

Example 3

This example shows the effects of free methanesulfonic acid on theconductivity of a solution containing high zinc ion concentration.Solutions of Zn(CH₃SO₃)₂ were prepared at a constant 32.5 g/l Zn⁺²concentration and free CH₃SO₃H varying from 0 to 500 g/l. Each solutionwas heated to 65° C. and the conductivity recorded in mS/cm as shown inthe following table.

32.5 g/l Zn++, 32.5 g/l Zn++, 32.5 g/l Zn++, 32.5 g/l Zn++, 32.5 g/lZn++, 32.5 g/l Zn++, 0 g/l CH₃SO₃H 100 g/l CH₃SO₃H 200 g/l CH₃SO₃H 300g/l CH₃SO₃H 400 g/l CH₃SO₃H 500 g/l CH₃SO₃H 20° C. 55.6 163.5 224 219209 150.2 25° C. 62.7 179.2 240 234 210 151.1 30° C. 69.7 199.3 260 256210 159 35° C. 76.7 212 281 278 214 158.3 40° C. 83.7 227 305 302 218158.1 45° C. 91 244 327 323 224 158.7 50° C. 96.4 260 348 346 229 158.655° C. 106.2 276 366 374 235 158.4 60° C. 113.1 291 387 391 239 157.965° C. 119.4 302 406 409 243 157.8

The data shows an increase in conductivity with temperature for eachelectrolyte below 400 g/l free MSA, an increase in conductivity withfree acid up to 300 g/l then a decrease in conductivity, a largerincrease in conductivity going from 0 to 100 g/l free acid compared toan increase in free acid from 100 to 200 g/l or from 200 to 300 g/l.Therefore, the zinc acid electrolyte can be operated at 300 g/l freeacid, or less, without significant detrimental effects on conductivity.

Example 4

This example shows the effects of free methanesulfonic acidconcentration on the cathode efficiency for zinc deposition in solutionscontaining high free zinc ion concentration.

Solutions of Zn(CH₃SO₃)₂ were prepared at a constant 65 g/l Zn⁺²concentration and free CH₃SO₃H varying from 0 to 300 g/l. Each solutionwas heated to 65° C. and the zinc was deposited on low carbon steel at30 A/dm² and 60 A/dm². The data in the following table shows the cathodeefficiency is high and commercially acceptable at 0 and 100 g/l freeacid but drops off considerably at 200 and 300 g/l free methanesulfonicacid.

65 g/l Zn⁺⁺/0 g/l 65 g/l Zn⁺⁺/100 g/l 65 g/l Zn⁺⁺/200 g/l 65 g/lZn⁺⁺/300 g/l CH₃SO₃H CH₃SO₃H CH₃SO₃H CH₃SO₃H Original Weight 8.49168.4557 8.5237 8.192 Final Weight 8.5882 8.5509 8.5705 8.2044 CathodeEfficiency (30 A/dm²) 95.10% 93.72% 46.07% 8.55% Appearance Light GrayLight Gray Light Gray Light Gray Cell Voltage 2.35 1.06 0.73 0.73Original Weight 8.3091 8.3626 8.2063 8.4544 Final Weight 8.5077 8.55558.348 8.4926 Cathode Efficiency (60 A/dm²) 97.76% 94.95% 69.75% 37.61%Appearance Light Gray Light Gray Light Gray Light Gray Cell Voltage 4.222.05 1.57 1.52

Example 5

This example shows the effects of boric acid concentration and freemethanesulfonic acid concentrations on the conductivity of a solutioncontaining zinc ion. Solutions of Zn(CH₃SO₃)₂ were prepared at aconstant 65 g/l Zn⁺² concentration and free CH₃SO₃H varying from 0 to300 g/l. Each solution was heated to 65° C. and the conductivityrecorded in mS/cm as shown in the following table.

65 g/l Zn⁺⁺/ 65 g/l Zn⁺⁺/100 g/l 65 g/l Zn⁺⁺/200 g/l 65 g/l Zn⁺⁺/300 g/l0 g/l CH₃SO₃H + 70 g/l CH₃SO₃H + 70 g/l Ce⁺³ + 0 g/l CH₃SO₃H + 70 g/lCe⁺³ + 0 g/l CH₃SO₃H + 70 g/l Ce⁺³ + 0 g/l Ce⁺³ + 0 g/l H₃BO₃ H₃BO₃H₃BO₃ H₃BO₃ 20° C. 81.2 141.4 156 135.1 25° C. 90.6 158.2 169.9 150.830° C. 97.4 168.5 190.5 165.8 35° C. 108.6 183.5 204 182.2 40° C. 116.1198.2 221 201 45° C. 127.6 214 238 216 50° C. 135.4 228 257 234 55° C.147.8 242 274 253 60° C. 155.1 257 293 271 65° C. 163.1 271 307 288 65g/l Zn⁺⁺/ 0 g/l CH₃SO₃H + 70 g/l 65 g/l Zn⁺⁺/100 g/l 65 g/l Zn⁺⁺/200 g/l65 g/l Zn⁺⁺/300 g/l Ce⁺³ + 10 g/l CH₃SO₃H + 70 g/l Ce⁺³ + 10 g/lCH₃SO₃H + 70 g/l Ce⁺³ + 10 g/l CH₃SO₃H + 70 g/l Ce⁺³ + 10 g/l H₃BO₃H₃BO₃ H₃BO₃ H₃BO₃ 20° C. 78.4 130.1 142.4 123.2 25° C. 86.5 142.1 155.2134.5 30° C. 95.6 156.4 171.3 148.8 35° C. 105.3 170.2 188.5 167.5 40°C. 114.6 186.4 201 188.2 45° C. 123.1 201 222 201 50° C. 131.2 216 242219 55° C. 143.5 232 258 237 60° C. 153.9 248 271 259 65° C. 165.1 262287 274 65 g/l Zn⁺⁺/ 0 g/l CH₃SO₃H + 70 g/l 65 g/l Zn⁺⁺/100 g/l 65 g/lZn⁺⁺/200 g/l 65 g/l Zn⁺⁺/300 g/l Ce⁺³ + 25 g/l CH₃SO₃H + 70 g/l Ce⁺³ +25 g/l CH₃SO₃H + 70 g/l Ce⁺³ + 25 g/l CH₃SO₃H + 70 g/l Ce⁺³ + 25 g/lH₃BO₃ H₃BO₃ H₃BO₃ H₃BO₃ 20° C. 79.2 121.5 133.4 113.6 25° C. 85.6 131.3143.2 121.2 30° C. 92.7 145.1 154.6 132.5 35° C. 101.2 152.5 171.8 149.240° C. 110.7 172.1 187.4 163.2 45° C. 119.3 180.2 202 177.2 50° C. 128.5196.4 217 193.2 55° C. 137.8 214 238 211 60° C. 148.1 234 270 234 65° C.158.6 251 284 255 65 g/l Zn⁺⁺/ 0 g/l CH₃SO₃H + 70 g/l 65 g/l Zn⁺⁺/100g/l 65 g/l Zn⁺⁺/200 g/l 65 g/l Zn⁺⁺/300 g/l Ce⁺³ + 50 g/l CH₃SO₃H + 70g/l Ce⁺³ + 50 g/l CH₃SO₃H + 70 g/l Ce⁺³ + 50 g/l CH₃SO₃H + 70 g/l Ce⁺³ +50 g/l H₃BO₃ H₃BO₃ H₃BO₃ H₃BO₃ 20° C. 74.2 110.3 114.1 98.4 25° C. 81.2120.7 120.2 107.1 30° C. 88.7 132.3 135.1 119.4 35° C. 95.8 145.1 147.1133.7 40° C. 104.2 156.5 161.6 145.5 45° C. 111.9 167.2 173.9 157.1 50°C. 120.8 179.8 189.3 169.1 55° C. 130.1 193.8 205 183.1 60° C. 138.1 214226 201 65° C. 147.9 223 242 220

The boric acid had a small effect on the conductivity particularly atthe lower boric acid concentrations.

Example 6

This example shows the effects of boric acid and free methanesulfonicacid concentrations on the cathode efficiency for zinc deposition insolutions containing high free zinc ion concentration.

Solutions of Zn(CH₃SO₃)₂ were prepared at a constant 65 g/l Zn⁺²concentration and 20 g/l boric acid was added and free CH₃SO₃H varyingfrom 0 to 300 g/l N. Each solution was heated to 65° C. and the zinc wasdeposited on low carbon steel at 30 A/dm² and 60 A/dm². The data in thefollowing table shows the cathode efficiency is high even at 300 g/lfree methanesulfonic acid.

65 g/l Zn⁺⁺/ 65 g/l Zn⁺⁺/100 g/l 65 g/l Zn⁺⁺/200 g/l 65 g/l Zn⁺⁺/300 g/l0 g/l CH₃SO₃H CH₃SO₃H/20 g/l H₃BO₃ CH₃SO₃H/20 g/l H₃BO₃ CH₃SO₃H/20 g/lH₃BO₃ Original Weight 8.6218 8.4511 8.3278 8.4332 Final Weight 8.77218.5513 8.4133 8.5171 Cathode Efficiency (30 A/dm²) 98.74% 98.64% 84.17%82.60% Appearance Light Gray Light Gray Light Gray Light Gray CellVoltage 2.38 1.24 1.01 0.9 Original Weight 8.5532 8.4611 8.3298 8.5475Final Weight 8.7351 8.6512 8.5131 8.7181 Cathode Efficiency (60 A/dm²)89.54% 93.57% 90.23% 83.97% Appearance Light Gray Light Gray Light GrayLight Gray Cell Voltage 4.25 2.22 1.7 1.64

Example 7

This example shows the effects of trifluoromethanesulfonate, lithiumsalt, concentration and free methanesulfonic acid concentrations on theconductivity of a solution containing zinc ion. Solutions of Zn(CH₃SO₃)₂were prepared at a constant 65 g/l Zn⁺² concentration and free CH₃SO₃Hvarying from 0 to 300 g/l. Each solution was heated to 65° C. and theconductivity recorded in mS/cm as shown in the following table.

65 g/l Zn⁺⁺/ 65 g/l Zn⁺⁺/100 g/l 65 g/l Zn⁺⁺/200 g/l 65 g/l Zn⁺⁺/300 g/l0 g/l CH₃SO₃H + 70 g/l CH₃SO₃H + 70 g/l Ce⁺³ + 14 g/l CH₃SO₃H + 70 g/lCe⁺³ + 14 g/l CH₃SO₃H + 70 g/l Ce⁺³ + 14 g/l Ce⁺³ + 14 g/l Ce⁺⁴ + 0 g/lCe⁺⁴ + 0 g/l Ce⁺⁴ + 0 g/l Ce⁺⁴ + 0 g/l LiCF₃SO₃ LiCF₃SO₃ LiCF₃SO₃LiCF₃SO₃ 20° C. 83.7 140.2 159.2 138.8 25° C. 91.7 156.2 176.6 156.5 30°C. 101.4 171.4 194.1 174.5 35° C. 110.9 190 216 188.1 40° C. 120.2 203230 205 45° C. 129.6 218 250 225 50° C. 139.8 235 270 240 55° C. 149 250285 258 60° C. 159.2 264 304 277 65° C. 170 278 319 295 65 g/l Zn⁺⁺/ 65g/l Zn⁺⁺/100 g/l 65 g/l Zn⁺⁺/200 g/l 65 g/l Zn⁺⁺/300 g/l 0 g/l CH₃SO₃H +70 g/l CH₃SO₃H + 70 g/l Ce⁺³ + 14 g/l CH₃SO₃H + 70 g/l Ce⁺³ + 14 g/lCH₃SO₃H + 70 g/l Ce⁺³ + 14 g/l Ce⁺³ + 14 g/l Ce⁺⁴ + 10 g/l Ce⁺⁴ + 10 g/lCe⁺⁴ + 10 g/l Ce⁺⁴ + 10 g/l LiCF₃SO₃ LiCF₃SO₃ LiCF₃SO₃ LiCF₃SO₃ 20° C.76.2 135 140.2 135.4 25° C. 84.7 149.3 152.4 148.9 30° C. 94 165.2 170.2161.1 35° C. 104.2 179.8 183.5 179.4 40° C. 112.2 195.8 199.7 196.1 45°C. 121.6 212 219 214 50° C. 131.1 228 238 233 55° C. 140.5 244 259 25360° C. 151 258 275 270 65° C. 162.2 275 295 287 65 g/l Zn⁺⁺/ 65 g/lZn⁺⁺/100 g/l 65 g/l Zn⁺⁺/200 g/l 65 g/l Zn⁺⁺/300 g/l 0 g/l CH₃SO₃H + 70g/l CH₃SO₃H + 70 g/l Ce⁺³ + 14 g/l CH₃SO₃H + 70 g/l Ce⁺³ + 14 g/lCH₃SO₃H + 70 g/l Ce⁺³ + 14 g/l Ce⁺³ + 014 g/l Ce⁺⁴ + 25 g/l Ce⁺⁴ + 25g/l Ce⁺⁴ + 25 g/l Ce⁺⁴ + 25 g/l LiCF₃SO₃ LiCF₃SO₃ LiCF₃SO₃ LiCF₃SO₃ 20°C. 76.2 129.2 138.1 129.4 25° C. 84.2 141.2 152.3 142.2 30° C. 91.1156.6 165 158.3 35° C. 101.1 174.2 181 173 40° C. 109.8 189.2 197.5191.3 45° C. 119.7 194.5 215 208 50° C. 129.7 216 232 225 55° C. 138.9232 250 241 60° C. 149.8 249 273 259 65° C. 160.2 263 287 275 65 g/lZn⁺⁺/ 65 g/l Zn⁺⁺/ 65 g/l Zn⁺⁺/ 65 g/l Zn⁺⁺/ 0 N CH₃SO₃H + 70 g/l 1 NCH₃SO₃H + 70 g/l 2 N CH₃SO₃H + 70 g/l 3 N CH₃SO₃H + 70 g/l Ce⁺³ + 14 g/lCe⁺⁴ + 50 g/l Ce⁺³ + 14 g/l Ce⁺⁴ + 50 g/l Ce⁺³ + 14 g/l Ce⁺⁴ + 50 g/lCe⁺³ + 14 g/l Ce⁺⁴ + 50 g/l LiCF₃SO₃ LiCF₃SO₃ LiCF₃SO₃ LiCF₃SO₃ 20° C.73.2 116.3 129.2 112.4 25° C. 82.2 129.2 145.4 124 30° C. 90.6 141.2162.1 131 35° C. 105.3 154.6 181.2 154.2 40° C. 109.2 169.8 196 171.245° C. 120.8 185.4 211 187 50° C. 130.7 201 227 202 55° C. 140.4 216 244218 60° C. 151.8 233 260 236 65° C. 160.8 248 275 254

The lithium trifluoromethanesulfonate salt had a small effect on theconductivity particularly at the lower concentrations.

Example 8

This example shows the effects of free methanesulfonic acidconcentration on the cathode efficiency for zinc deposition with Ce⁺³ions present.

Solution of Zn(CH₃SO₃)₂ were prepared at a constant 65 g/l Zn⁺² and 70g/l Ce⁺³ (added as the methanesulfonate salt) concentrations and freeCH₃SO₃H varying from 0 to 300 g/l N. Each solution was heated to 65° C.and the zinc was deposited on low carbon steel at 30 A/dm² and 60 A/dm².The data in the following table shows the cathode efficiency is high andcommercially acceptable at 0 and 100 g/l free acid and high currentdensity but drops off considerably at 200 and 300 g/l freemethanesulfonic acid.

65 g/l Zn⁺⁺/ 65 g/l Zn⁺⁺/ 65 g/l Zn⁺⁺/ 65 g/l Zn⁺⁺/ 0 N CH₃SO₃H + 70 g/l1 N CH₃SO₃H + 70 g/l 2 N CH₃SO₃H + 70 g/l 3 N CH₃SO₃H + 70 g/l Ce⁺³ Ce⁺³Ce⁺³ Ce⁺³ Original Weight 8.293 8.7048 8.6407 8.6837 Final Weight 8.38778.7702 8.6967 8.6971 Cathode Efficiency (30 A/dm²) 93.23% 64.38% 55.13%26.38% Appearance Light Gray Light Gray Light Gray Light Gray CellVoltage 1.74 1.26 0.71 0.83 Original Weight 8.5111 8.0504 8.435 8.1435Final Weight 8.7113 8.2337 8.5739 8.1937 Cathode Efficiency (60 A/dm²)98.54% 90.23% 68.37% 49.42% Appearance Light Gray Light Gray Light GrayLight Gray Cell Voltage 3.26 2.24 1.76 2.28

Example 9

This example shows the effects of free methanesulfonic acidconcentration on the cathode efficiency for zinc deposition with Ce⁺³and Ce⁺⁴ ions present.

Solution of Zn(CH₃SO₃)₂ were prepared at a constant 65 g/l Zn⁺² and 70g/l Ce+3 and 0.1 M Ce⁺⁴ (added as the methanesulfonate salts)concentrations and free CH₃SO₃H varying from 0 to 300 g/l. Each solutionwas heated to 65° C. and the zinc was deposited on low carbon steel at30 A/dm² and 60 A/dm². The data in the following table shows the cathodeefficiency is high and commercially acceptable at 0 and 100 g/l freeacid and low or high current densities but drops off considerably at 200and 300 g/l free methanesulfonic acid.

65 g/l Zn⁺⁺/0 g/l 65 g/l Zn⁺⁺/100 g/l 65 g/l Zn⁺⁺/200 g/l CH₃SO₃H +CH₃SO₃H + CH₃SO₃H + 65 g/l Zn⁺⁺/300 g/l 70 g/l Ce⁺³ + 14 g/l 70 g/lCe⁺³ + 14 g/l 70 g/l Ce⁺³ + 14 g/l CH₃SO₃H + 70 g/l Ce⁺³ + 14 g/l Ce⁺⁴Ce⁺⁴ Ce⁺⁴ Ce⁺⁴ Original Weight 8.7301 8.6603 8.1086 8.3527 Final Weight8.8215 8.7471 8.1695 8.3627 Cathode Efficiency (30 A/dm²) 89.98% 85.45%59.95% 19.69% Appearance Light Gray Light Gray Light Gray Light GrayCell Voltage 1.73 1.42 1.23 1.68 Original Weight 8.0713 8.1279 8.56458.5081 Final Weight 8.2684 8.3174 8.6992 8.55 Cathode Efficiency (60A/dm²) 97.02% 93.28% 66.30% 41.25% Appearance Light Gray Light GrayLight Gray Light Gray Cell Voltage 3.57 2.88 2.21 2.7

Example 10

This example shows the effects of cerric salt solubility in varyingconcentrations of methanesulfonic acid. Aqueous solutions were preparedcontaining 65 g/l Zn⁺² and 70 g/l Ce⁺³ from their correspondingmethanesulfonate salts. Cerric methanesulfonate was added incrementallyand allowed to dissolve for at least 24 hours. A yellow precipitatemarked the onset of Ce⁺⁴ saturation.

Free Free CH₃SO₃H: CH₃SO₃H: Free CH₃SO₃H: 100 g/l 200 g/l 300 g/l TotalSoluble Ce⁺⁴ (g/l) 54.79 20.87 4.06 Total Soluble Ce⁺⁴ (M) 0.391 0.1490.029

The solubility of Ce⁺⁴ is less as the concentration of free MSAincreases. To minimize cerric ion precipitation in an energy storagedevice and possibly clogging of membranes, separators, and porouselectrodes, it is advisable to operate the Zn—Ce cell with low free MSAand low Ce⁺⁴ concentration.

Example 11

This example shows the effects of cerric salt solubility in lowconcentrations of methanesulfonic acid. Aqueous solutions were preparedcontaining 65 g/l Zn⁺² and 70 g/l Ce⁺³ from their correspondingmethanesulfonate salts. Cerric methanesulfonate was added incrementallyand allowed to dissolve for at least 24 hours. A yellow precipitatemarked the onset of Ce⁺⁴ saturation.

Free Free CH₃SO₃H: CH₃SO₃H: Free CH₃SO₃H: 25 g/l 50 g/l 75 g/l TotalSoluble Ce⁺⁴ (g/l) 59.97 55.21 50.16 Total Soluble Ce⁺⁴ (M) 0.428 0.3940.358

Example 12

This example shows the effects of trace impurities on producing anunwanted odor during the dissolution of active metals. Zinc metal wasdissolved into purified 70% MSA until the zinc ion concentration was 65g/l. No odor was detected during the dissolution of zinc metal. Zincmetal was also dissolved into 70% MSA containing 10 mg/l of methylmethanethiosulfonate, MMTS, (CH₃SO₂SCH₃). During dissolution, a pungentodor was detected.

1. An aqueous solution for an electrochemical energy storage devicewhich comprises (a) a high purity sulfonic acid with a low concentrationof low valent sulfur compounds or higher valent sulfur compoundssusceptible to reduction comprising a sum total concentration ofdimethyldisulfide (CH₃SSCH₃), dimethylsulfide (CH₃SCH₃), dimethylsulfone(CH₃SO₂CH₃), trichioromethyl methylsulfone (CH₃SO₂CCl₃), dichloromethylmethylsulfone (CH₃SO₂CHCl₂), methyl methanethiosulfonate (CH₃SO₂SCH₃),and methyl methanesulfonate (CH₃SO₃CH₃) of less than about 50 mg/l, (b)a metal or metals in an oxidized state capable of being reduced to thezero valent oxidation state, (c) a metal that is in an oxidized statethat is incapable of being reduced to its metallic state, and optionally(d) a buffering agent and optionally (e) conductivity salts.
 2. Thesolution of claim 1 wherein said high purity sulfonic acid is derivedfrom an alkyl monosulfonic acid, an alkyl polysulfonic acid, an arylmono or polysulfonic acid or mixture thereof.
 3. The solution of claim 1wherein said high purity sulfonic acid is introduced as:

wherein R, R′ and R″ are the same or different and each independentlymay be hydrogen, phenyl, Cl, F, Br, I, CF₃ or a lower alkyl group suchas (CH₂)n where n is from 1 to 7 and that is unsubstituted orsubstituted by oxygen, Cl, F, Br, I, CF₃, —SO₂OH.
 4. The solution ofclaim 1 wherein the sulfonic acid is methanesulfonic acid,ethanesulfonic acid, propanesulfonic acid, methanedisulfonic acid,monochloromethanedisulfonic acid, dichloromethanedisulfonic acid,1,1-ethanedisulfonic acid, 2-chloro-1,1-ethanedisulfonic acid,1,2-dichloro-1,1-ethanedisulfonic acid, 1,1-propanedisulfonic acid,3-chloro-1,1-propanedisulfonic acid, 1,2-ethylene disulfonic acid,1,3-propylene disulfonic acid, trifluoromethanesulfonic acid,butanesulfonic acid, perfluorobutanesulfonic acid, pentanesulfonic acid,phenyl sulfonicacid, phenolsulfonic acid, para-toulenesulfonic acid, andxylenesulfonic acid or mixtures thereof.
 5. The solution of claim 1wherein said high purity sulfonic acid has a concentration of from about1 to 1480 grams per liter of solution.
 6. The solution of claim 1wherein said high purity sulfonic acid has a concentration of from about10 to about 1200 grams per liter of solution.
 7. The solution of claim 1wherein said high purity sulfonic acid has a concentration of from about30 to about 300 grams per liter of solution.
 8. The solution of claim 1wherein the pH is between 0.5 to
 4. 9. The solution of claim 1 whereinsaid high purity sulfonic acid is a mixture of sulfonic acids.
 10. Thesolution of claim 1 wherein said buffering agent is added to modulatethe pH of the solution.
 11. The solution of claim 10 wherein saidbuffering agent is boric acid.
 12. The solution of claim 1 wherein aconductivity salt is added to the solution.
 13. The solution of claim 12wherein said conductivity salt is an ammonium ion.
 14. The solution ofclaim 1 wherein the metals are introduced as a metal salt of a highpurity alkyl or aryl sulfonic acid of formula:

wherein R, R′ and R″ are the same or different and each independentlymay be hydrogen, phenyl, Cl, F, Br, I, CF₃ or a lower alkyl group suchas (CH₂)n where n is from 1 to 7 and that is unsubstituted orsubstituted by oxygen, Cl, F, Br, I, CF₃, —SO₂OH and x varies from 1 to4 and M is a metal from the 2B or lanthanide groups of the periodictable.
 15. The solution of claim 14 wherein an individual metal salt isemployed at a concentration of from about 1 to about 500 grams per literof solution.
 16. The solution of claim 14 wherein an individual metalsalt is employed at a concentration of from about 10 to about 400 gramsper liter of solution.
 17. The solution of claim 14 wherein anindividual metal salt is employed at a concentration of from about 30 toabout 150 grams per liter of solution.
 18. The solution of claim 14wherein said high purity sulfonic acid is methanesulfonic acid,ethanesulfonic acid, propanesulfonic acid, trifluoromethanesulfonic acidor mixtures thereof.
 19. The solution of claim 14 wherein the metalsulfonic acid salt is zinc methanesulfonate.
 20. The solution of claim14 wherein the metal sulfonic acid salt is cerrous methanesulfonate. 21.The solution of claim 14 wherein the metal sulfonic acid salt is cerricmethanesulfonate.
 22. The solution of claim 14 wherein the metalalkanesulfonic acid salt is vanadium methanesulfonate.
 23. A process ofmaking metal-sulfonate solutions by dissolving pure metal, metalcarbonate, metal oxide or other metal salts into a high purity sulfonicacid according to claim 1 wherein the metal ion concentration variesfrom about 1 g/l to about 150 g/l.
 24. A process for the deposition of ametal from the solution of claim 1 comprising passing an electriccurrent through the solution to electroplate a metal or a metal alloyunto a substrate.
 25. The process of claim 24 wherein the substrate isan inert electrode of steel, copper or copper-alloy, nickel ornickel-alloy, cobalt or cobalt alloy, a refractory metal or oxide,carbon or an organic substrate.
 26. The process of claim 25 wherein thehigh purity sulfonic acid is methanesulfonic acid.
 27. The process ofclaim 24 wherein the solution contains a mixture of sulfonic acids andother inorganic and organic acids.
 28. The process of claim 24 whereindirect current, pulsed current or periodic reverse current is used. 29.The process of claim 24 wherein a soluble, insoluble or inert anode isused.
 30. The process of claim 24 wherein the temperature of thesolution is between about 20° C. to 95° C.
 31. The process of claim 24wherein the metal is pure metal or a metal alloy with a metal from Group2B, and the lanthanide metals of the periodic table or combinationsthereof.